Notification of errors often requires
special handling by sendmail. When mail to a
mailing list fails, for example, sendmail looks
for the owner of that list. If it finds one, the owner, not the
sender, receives notification of the error. To differentiate error
notification addresses from ordinary sender and recipient addresses,
pre-V8.7 sendmail stored error addresses
separately in the qf file, one per
E line. Beginning with V8.7, this
E line is no longer used. Instead,
sendmail uses the S line.
The form of the E line in the
qf file looks like this:
Eaddr 
V8.6 and earlier
The E must begin the line. One or more addresses
can be entered on that same line. Whitespace and commas can surround
the individual addresses. Note, however, that
sendmail places only a single address on each
E line. There can be multiple E
lines. Each is processed in turn.
Each line is fully processed as it is read. That is, the line is
scanned for multiple addresses. Each address that is found is
alias-expanded. Each resulting new address is processed by rule sets
3 and 0 to resolve a delivery agent for each.
If an alias expands to a program or a file (text that begins with a
/ or | character), that text is
sent out in the delivered message's
Errors-To: line in that form. This can cause
confusion when the message is later processed and bounced at the
receiving site.
